java虚拟机分析和优化.ppt

Java虚拟机分析与优化;Overview;JVM BasicsHighest Level Overview;JVM BasicsWhich JVM do I have?;JVM BasicsThe Overall Java Application Stack;JVM BasicsJIT Basics from a performance perspective;Overview;Overview of IBM’s J9 JVMWhat is the J9 JVM?;Garbage collector enhancements Incorporates for the first time generational garbage collection Fine-grained locking of VM data structures Asynchronous compilation Compilation of Java methods proceeds on a background thread Other application threads do not have to wait to execute the method Improves startup time of heavily multithreaded applications on SMPs Compile-time optimizations to remove contention escape analysis, lock coarsening, … architectural support to limit its effect Superior JIT (Just in time) compiler Multiple optimization methods from application profiling to more intelligent and better code optimization algorithms;Superior Java application execution performance Just-In-Time (JIT) compiler technology Far improved over JDK 1.4.2 and Sun’s JIT Maximized performance with minimized runtime overhead multiple optimization levels, multiple recompilations of the same method, many new optimizations dynamic observation of the execution of code via profiling to aggressively improve hot code Interpreter profiling to adapt compilation to compiled methods for block reordering, loop unrolling, etc.;Overview;Memory Management / Garbage CollectionOverview;Memory Management / Garbage CollectionWhat factors effect memory performance the most;Memory Management / Garbage Collection Parallel VS Concurrent Collectors;IBM J9 JDK Platforms Memory management is configurable using four different policies with varying characteristics Optimize for Throughput – flat heap collector focused on maximum throughput Optimize for Pause Time – flat heap collector with concurrent mark and sweep to minimize GC pause time Generational Concurrent – divides heap into “nursery” and “tenured” segments providing fast collection for short lived objects. C